The present invention relates generally to narrow-profile, terminal block relays, and in particular, to a terminal block time delay relay.
This section of this document is intended to introduce various aspects of art that may be related to various aspects of the present invention described and/or claimed below. This section provides background information to facilitate a better understanding of the various aspects of the present invention. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art.
“European style” terminal blocks provide a method of electrical interconnection of industrial control components. These terminal blocks have a narrow and flat shape that allows them to be stacked together in close proximity when mounted on a DIN rail. When so stacked, wires may be received at terminals along the upper and lower edge of the terminal blocks.
The terminals allow connection to other wires connected to other terminals or to the leads of electrical components supported by the terminal block. Such electrical components may include fuses, indicator lights, and relays.
For a terminal block holding a relay (“a terminal block relay”), a replaceable relay is typically received by a socket at the front edge of the terminal block. The housings holding the relay or fuse are designed to have a width no greater than that of the terminal block, typically between 5 to 14 mm, to minimize space occupied on the DIN rail.
Programmable logic controllers (PLCs) are industrial computers used for the control of machines and processes. A PLC has input and output circuits that may connect to sensors and actuators on controlled machines and by executing a standard control language, such as relay ladder language, the PLC may read the inputs and according to the execution of the control program and provide outputs controlling the machine.
Terminal block relays are often used with a PLC, the latter which may be attached to the same DIN mounting rail on which the terminal block relays are mounted. Outputs from the PLC are connected to the coils of terminal block relays whose outputs in turn connect to the desired machine actuator to provide a form of isolation.
One particular type of relay useful in industrial control applications is a time delay relay. Time delay relays have various modes of operation, but generally, the activation or deactivation of the relay is delayed by predetermined time interval. Typically, time delay relays in narrow profile applications include a single package that holds the timing circuitry, the coil, and the outputs.
A time delay relay typically has a plurality of settings, including delay mode, range, and delay. Adjustment dials are provided on the time delay relay for altering these settings. Due to the need for providing access to the adjustment dials, terminal blocks for time delay relays are typically larger than their standard relay counterparts, thereby consuming more panel space within the control cabinet.
In a time delay relay, the components typically prone to usage-related failure are the coil and switching device. Because the timing circuitry is integrated with the relay circuitry (e.g., coil, switch, and outputs), the entire time delay relay must be replaced due to the failure of the moving parts of the relay circuitry. The settings of the replacement relay must then be reconfigured to provide the proper mode, range, and delay setting.